Refrigeration-heating circuit



United States Patent .Iersey Fried Aug. 14, 1961, Sex. No. 131,241 6 Claims. (Cl. 165-62) This invention relates to improvements in process and apparatus for liquefying gases and more particularly to the use of nitrogen in a closed cycle refrigeration and heat exchange circuit for temperature control of a load.

The use of nitrogen as a refrigerant for unusually low temperature such as 345 F. has been known for many years. More recently the use of nitrogen has been proposed for certain loads where low temperatures are required and where the heat to be absorbed is relatively large and may fluctuate over substantial limits. However, in certain equipment, where heat transfer rates vary widely and the range of temperatures of heat release vary radically, the usual temperature control using a nitrogen refrigerant also for heating has been considered inadequate and excessively expensive.

In accordance with my invention, I propose to use a gas liquefaction plant, such as for liquefaction and reliquefaction of nitrogen, and by the use of supplementary controls and equipment I can accomplish the entire range of temperature control and still utilize the piping, insulation, valves, compressors and instruments which are appropriate to the sub-cooling operation alone.

My invention has for its primary object the provision of a gas re-liquefier and liquefier circuit for use in load temperature control, which circuit includes supplementary equipment adapted to provide desired temperatures in the range of 450 F. to 345 F. whereby the temperature of the load may be maintained at a desired level or economically changed without thermal shock.

Further objects and advantages of my invention will appear from the following description of a preferred form of embodiment thereof, when taken in conjunction with the attached drawing which is illustrative thereof and in which the drawing is a schematic flow diagram of a refrigeration and heating circuit.

In accordance with my invention, the flow diagram includes a series of units which are integrated in a manner to accomplish in a most economical manner several heat exchange conditions required for a commercial operation.

The several conditions are as follows:

- Case 1Liquid refrigeration of the load.

Case 2Gas cooling of the load. Case 3-Liquid refrigerant production. Case 4Heating of the load.

Case 1 In accordance with a preferred form of embodiment of my invention when a load 45 is to be cooled tovthe very loW temperature and thus requires liquid refrigerant the gaseous refrigerant which enters the system at It} and passes through valve 90 is compressed by compressor 12 within the range of 100 to 2800 p.s.i.g. after which the refrigerant passes through valve 91 to heat exchanger 14 in which the heat of compression is removed. Valves 92,

'93, and 94. are normally closed.

3,161,232 Patented Dec. 15., 1964 The high pressure gaseous nitrogen at about ambient temperature is then passed by line 15 through a series of heat exchangers 16 and 18 from which it discharges at 19 at a relatively low temperature. Part of this gaseous nitrogen at the high pressure is passed through valve and then expanded in expander 20 substantially to the dew point corresponding to the suction pressure of compressor 12. At 30 p.s.i.a., this corresponds to about 304 F.

This gas then passes through valve 96 in line 21, and heat exchangers Z2 and 24 and thence through line 25, heat exchangers 18 and 16 and line 26 to the compressor suction. Valves 97 and are closed.

It is of course understood that the temperature obtained by the Joule-Thompson effect is a function of the suction head pressure of the compressor and the boiling level of the refrigerant. Ordinarily the higher the pressure, the higher the temperature.

The remainder of the high pressure gaseous nitrogen discharging at 19 passes through line 23 and valve 98, valve 7%) being closed, and thence through the heat exchangers 24 and 22 to further cool the nitrogen. This sub-cooled nitrogen, discharging through line 30 is then flashed in expansion valve 32 also to a pressure substantially that of the suction of compressor 12 (in this case 30 p.s.i.a.). This reduces the fluid to a liquid which is collected in storage tank 34. Vapors may beremoved from the storage tank through valve 99, line 36 and, as hereinafter described, returned to the gas line at 21 through valve 101) and line 43 or to a vent line 38 through valve 101.

Liquid nitrogen is removed from tank 34 through line 40 and circulated through valve 102 to the sub-cooler or condenser-vaporizer 42. The vapors are then returned through line 43 to the gas line 21, which as before mentioned, is interconnected through line 25 with the compressor suction line 26.

While specific temperatures have been given as an example of an operating unit, it is recognized that the temperature and pressure of a particular refrigerant are interrelated to the extent that changes in pressure have a substantially direct effect on temperature of a particular refrigerant and that the temperature-pressure condition will vary with different refrigerants.

The load 45 is suitably cooled by a separate closed refrigerant circuit with the low temperature refrigerant removed in line 46 from the sub-cooler or condenser-vaporizer 42 and pumped by pump 48 through valve 103 to the load 45 valves 104 and'1tl5, and 72 being closed and returned through valve 106, valve 9 1 being closed, and lines 66 and 50 to the sub-cooler or condenser-vaporizer'42. The, refrigerant in this closed circuit may be liquid nitrogen introduced into the circuit through the bypass line 52 under control of valve 107. Usually a drum 54 is provided for the return refrigerant from the load 45, and such drum is vented if necessary through valve 108.

It will thus be apparent that very low temperatures in the load are readily maintained by a typical heatexchange circuit.

Case 2 If it is desired to supply the load {35 with a gaseous rather than a liquid refrigerant to maintain a temperature of the loadin the range of ambient to 345 F. this is accomplished by bypassing a part of the higher temperature gas from heat exchanger 18 through line 28 and 60 with valve 71) open to blend with the cooled gas discharging in line 62 from expander 20. A part of this gas in line 62 is then conducted through valve 105 by line 641 with valve 96 closed into the load 45 and the rest is passed through valve 97 and line 25 back through heat exchangers 18 and 16 and return line 26 to the feed at line It '78 with recycle gas in line 26.

through line 66, valve 106 being closed passes through valve 72 and line68 to line and thus directly back,

through the heat exchangers 18 and 16 to the feed. 7 It will be understood that the operation of valves 70 and 72 will control the temperature of load 45. In this phase of the circuit, the heat exchangers 22 and 24 are not used but full advantage is taken of the overall piping, heat exchangers 16 and'18 and, of course, the compressor 12 and expander 20. 1 I 1 Case 3 The availability of the nitrogen-compression and reliquifaction apparatus and heat exchangers makes the refrigeration circuit particularly advantageous-for the production of liquid nitrogen for external use. In, this case, the circuit includes the makeup nitrogen feed line 10, open valve Ml, compressor 12, open valve 91, in line 86, cooler 14, feedline 15, heat exchangers 16 and 18, exit line 19, open valve 95, expander: 20, open valve 96, closed valve 70,intermediate line 21, the heat exchangers 22 and 24 closed valves 97 and 72 and the main gas return 25 through heat exchangers Band 16 and return'line Operating conditions are 'sub- 26 to compressor 12.

stantially the same as described for Casel.

.The liquid nitrogenjproduction is accomplished by drawing oif some of the cold nitrogen gas discharging'in line 19 from heat exchanger 18 and through line 28 with closed valve 70 and open valve- 98 and thence through To more clearly delineate the operations, the position of valves for the four conditions is as follows:

Case 1, Case 2, Case 3, Case 4, Valve liquid Gaseous 7 Liquid Heating Relrig Reirig'n Productn Open.

Do. Throttling. D0.

Open Throttling.

While I have shown a preferred form of embodiment of 'my' invention, I am aware that modifications may be H made thereto which are within the scope and spirit of Q the disclosureherein and of the claims appended hereinafter.

' 1. A heat exchange circuit for controlling the temheat exchangers 24- and 22'1and line 30 to expansion valve 32 and nitrogenreservoir 34. The liquid nitrogen Y may be removed from the reservoir 34 through line and drawn off as product at 75. The gaseous nitrogen removed overhead from reservoir 34 through valve 99' and line 36 is returned to line 21 from the expander 20 which with valve 96 open, conducts the gas back through heat exchangers" 22-and 24 and with valves 72 and 97' closed then through line 25 and heat exchangers 18 and 16 to line 26 whichinterconnects with the feed are.

It isto be noted in this case as well as the others that some of the gas from the discharge from the heat ex'-. changer 14 may be blended through line 77 and valve Case ,4

There are times in the operationof the load that complete scavenging or reheating is required.

In this circuit, the makeup nitrogen in line is valve '94 in 1ine 84 and recirculatedtback through cooler n 14 andvalve' 78 and lines 77 and 26 to the compressor 12. The' compressor 12 may also havea direct cooling circuit'through'line 86 and valve 91. j y I Itwill be apparentin this circuit that the temperature of discharge of the nitrogen from'the compressor 12'fwhich I'clairn: I

perature of a load which includes interconnected elements as follows: v

(a) a gaseous refrigerant compressor; I (b) means cornmuni cating with the compressor to remove theheat of compression from said refrigerant; 7

(c) a first pair of reversing exchangers to further cool said refrigerant; V (diam expander to sub-cool a portion of said refrigerant; (e) a second pair ing-the temperature or thehigh pressure refrigerant f to: the dew point by heat interchange with the subcooled portion of refrigerant;

(f) an expansion valve to expand. the high pressure refrigerant and form liquid refrigerant;

(g) a liquid refrigerant receiver in communication 1 with the expansion valve; I

(h) a separate heat exchange circuitfor the load including a refrigerant condensenin communication with the liquid refrigerant, an evaporator inheat 'of reversing exchangers for reducf 'frigerant through the separate circuit;

(i) and valve means communicating sub-cooled gaseoust refrigerant from the first mentioned heatex- ,7 change circuit into' the separate heat exchange cir cult; i

a 2, A'heat exchangecircuit as claimed in claim 1 having separatewithdrawal meanstfor removingfliquid refrig erant' from the first mentioned' -heat'exchange circuit.

may be as high'as 45O9TE t'can becooled downfby the a cooler 81) to provide a gas c'o'oling stream 82 which may vary from 459515. down to any oth d i temperature, in'the orderlofambient'.

It will thu -be'apparent each 'case; the same "compression and; heat' exchange .'equipment. is utilized and itflislmerely necessary to con- I trol the appropriate valvesand to supply more orlessiof j the nitrogen'or otherrefrigerant. The use of othernormally, gaseous materials can also be used where,theyare appropriate for the desired temperature ranges I required.

that I-have provided a simplified 110W and control for maintaining aiternperature in a load over. therange-of 345: F. to as high as 450 F; In

*throughthe load by 3. A heat exchange circuit as claimed in claim 1 having bypass conduits extending between the diseharge of the compressor and the inlet to the compressor and passing way of'the'separate heat exchange circuit.

4. A heat exchange circuit as claimed in claim 3'where- 1n the gaseous refrigerant is nitrogen andthe temperature of the load maybe varied between450; F. and -3 45 F.

'5. In a low temperature normally gaseous refrigerant perature as low as 345 F. 'havinga' compressor wherein the lgaseous xrefrrgerant is ;cor npresse,d,.jan intercooler wherein the heat of cornpressionis removed, and reversing exchangers i for further. cooling the cooled high pressure 7 exchange with the load, a pump to circulate rerefrigerant, expansion means for expanding a part of the further cooled refrigerant to form a lower pressure subcooled part, such sub-cooled part being passed in heat exchange with the remainder of the further cooled refrigerant at the high pressure to form a normally gaseous refrigerant portion at high pressure and at a temperature substantially at its dew point, means to expand such portion at the dew point to form a refrigerant liquid, the improvement wherein a separate heat exchange circuit includes a condenser in heat exchange with the refrigerant liquid and an evaporator in heat exchange with the load and a part of the further cooled low pressure refrigerant is bypassed directly into the separate heat exchange circuit through the load.

6. In a low temperature normally gaseous refrigerant circuit as claimed in claim 5 including bypass connections around the reversing heat exchangers whereby compressed gaseous refrigerant is passed directly into the separate heat exchange circuit through the load.

References Cited in the file of this patent UNITED STATES PATENTS 2,509,034 Claitor et al May 23, 1950 2,522,787 Hughes Sept. 19, 1950 2,553,623 Zumbro May 22, 1951 2,737,032 Latham Mar. 6, 1956 2,760,356 Sixsmith Aug. 28, 1956 2,928,255 Harnish Mar. 15, 1960 FOREIGN PATENTS 831,613 Great Britain Mar. 30, 1960 

1. A HEAT EXCHANGE CIRCUIT FOR CONTROLLING THE TEMPERATURE OF A LOAD WHICH INCLUDES INTERCONNECTED ELEMENTS AS FOLLOWS: (A) A GASEOUS REFRIGERANT COMPRESSOR; (B) MEANS COMMUNICATING WITH THE COMPRESSOR TO REMOVE THE HEAT OF COMPRESSION FROM SAID REFRIGERANT; (C) A FIRST PAIR OF REVERSING EXCHANGERS TO FURTHER COOL SAID REFRIGERANT; (D) AN EXPANDER TO SUB-COOL A PORTION OF SAID REFRIGERANT; (E) A SECOND PAIR OF REVERSING EXCHANGERS FOR REDUCING THE TEMPERATURE OF THE HIGH PRESSURE REFRIGERANT TO THE DEW POINT BY HEAT INTERCHANGE WITH THE SUBCOOLED PORTION OF REFRIGERANT; (F) AN EXPANSION VALVE TO EXPAND THE HIGH PRESSURE REFRIGERANT AND FORM LIQUID REFRIGERANT; (G) A LIQUID REFRIGERANT RECEIVER IN COMMUNICATION WITH THE EXPANSION VALVE; (H) A SEPARATE HEAT EXCHANGE CIRCUIT FOR THE LOAD IN CLUDING A REFRIGERANT CONDENSER IN COMMUNICATION WITH THE LIQUID REFRIGERANT, AN EVAPORATOR IN HEAT EXCHANGE WITH THE LOAD, A PUMP TO CIRCULATE REFRIGERANT THROUGH THE SEPARATE CIRCUIT; (I) AND VALVE MEANS COMMUNICATING SUB-COOLED GASEOUS REFRIGERANT FROM THE FIRST MENTIONED HEAT EXCHANGE CIRCUIT INTO THE SEPARATE HEAT EXCHANGE CIRCUIT. 